Brake system and method of operating
First Claim
1. A vehicle braking system comprising:
- a master cylinder having an input side configured to receive an input from a brake pedal and an output side configured to provide a master cylinder output,at least one braking circuit having at least one wheel cylinder and a brake pressure generator separate from the brake pedal;
a simulator circuit including a pedal feel simulator coupled to the master cylinder output side through a switchable simulator valve, the pedal feel simulator providing a reaction force to the brake pedal when the switchable simulator valve is in an open position;
at least one normally-open isolation valve operable to close and isolate the at least one braking circuit from the master cylinder and the simulator circuit;
a primary pressure sensor operable to generate a braking request signal responsive to the input from the brake pedal; and
a controller programmed to activate the brake pressure generator to apply a braking force to the at least one wheel cylinder of the braking circuit based on the braking request signal from the primary pressure sensor, the controller further being programmed to close the at least one normally-open isolation valve during activation of the brake pressure generator so that the master cylinder is coupled to the simulator circuit and decoupled from the braking circuit;
wherein the controller is further programmed to identify an abnormal value for the braking request signal from the primary pressure sensor, and in response, the controller is programmed to open the at least one normally-open isolation valve and to observe a relationship between brake pedal actuation and pressure generated at the master cylinder output side using a secondary pressure sensor that is positioned in the braking circuit such that the controller determines whether the abnormal value is indicative of a primary pressure sensor malfunction or indicative of a malfunction of at least one of the pedal feel simulator and the switchable simulator valve.
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Accused Products
Abstract
A vehicle braking system includes a brake pedal, master cylinder, a braking circuit with a wheel cylinder, and a brake pressure generator. A pedal feel simulator is coupled to the master cylinder output side through a switchable valve, the pedal feel simulator providing a reaction force. An isolation valve closes to isolate the braking circuit from the master cylinder and the simulator circuit. A primary pressure sensor generates a braking request signal responsive to the brake pedal. A controller activates the brake pressure generator to apply a braking force to the wheel cylinder based on the braking request signal. The controller identifies an abnormal value from the primary pressure sensor and couples the pedal feel simulator with a secondary pressure sensor within the braking circuit to determine whether the abnormal value indicates a primary pressure sensor malfunction or a malfunction of the pedal feel simulator or the switchable simulator valve.
33 Citations
19 Claims
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1. A vehicle braking system comprising:
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a master cylinder having an input side configured to receive an input from a brake pedal and an output side configured to provide a master cylinder output, at least one braking circuit having at least one wheel cylinder and a brake pressure generator separate from the brake pedal; a simulator circuit including a pedal feel simulator coupled to the master cylinder output side through a switchable simulator valve, the pedal feel simulator providing a reaction force to the brake pedal when the switchable simulator valve is in an open position; at least one normally-open isolation valve operable to close and isolate the at least one braking circuit from the master cylinder and the simulator circuit; a primary pressure sensor operable to generate a braking request signal responsive to the input from the brake pedal; and a controller programmed to activate the brake pressure generator to apply a braking force to the at least one wheel cylinder of the braking circuit based on the braking request signal from the primary pressure sensor, the controller further being programmed to close the at least one normally-open isolation valve during activation of the brake pressure generator so that the master cylinder is coupled to the simulator circuit and decoupled from the braking circuit; wherein the controller is further programmed to identify an abnormal value for the braking request signal from the primary pressure sensor, and in response, the controller is programmed to open the at least one normally-open isolation valve and to observe a relationship between brake pedal actuation and pressure generated at the master cylinder output side using a secondary pressure sensor that is positioned in the braking circuit such that the controller determines whether the abnormal value is indicative of a primary pressure sensor malfunction or indicative of a malfunction of at least one of the pedal feel simulator and the switchable simulator valve. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 18)
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11. A method of operating a vehicle braking system, the method comprising:
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receiving an input from a brake pedal at an input side of a master cylinder and providing a master cylinder output corresponding to the brake pedal input at an output side of the master cylinder output; closing, by a controller signal, at least one normally-open isolation valve to isolate the output side of the master cylinder from at least one braking circuit having at least one wheel cylinder; opening, by a controller signal, a switchable simulator valve to open a fluid connection between the master cylinder output side and a simulator circuit including a pedal feel simulator to provide a reaction force to the brake pedal; generating a braking request signal with a primary pressure sensor responsive to the input from the brake pedal, the braking request signal being sent to a controller; driving a brake pressure generator of the at least one braking circuit, separate from the brake pedal, with the controller responsive to the braking request signal to achieve braking at the at least one wheel cylinder; identifying with the controller an abnormal value for the braking request signal from the primary pressure sensor; sending a controller signal, in response to identifying the abnormal value, to open the at least one normally-open isolation valve and to observe a relationship between brake pedal actuation and pressure generated at the master cylinder output side using a secondary pressure sensor that is positioned in the braking circuit; and determining with the controller, based on the observed relationship, whether the abnormal value is indicative of a primary pressure sensor malfunction or indicative of a malfunction of at least one of the pedal feel simulator and the switchable simulator valve. - View Dependent Claims (12, 13, 14, 15, 16, 17, 19)
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Specification